Nanoparticles Penetrate into the Multicellular Spheroid-on-Chip: Effect of Surface Charge, Protein Corona, and Exterior Flow.

Nanoparticles (NPs) are widely studied as tumor targeted vehicles. The penetration of NPs into the tumor is considered as a major barrier for delivery of NPs into tumor cell and a big challenge to translate NPs from lab to the clinic. The objective of this study is to know how the surface charge of NPs, the protein corona surrounding the NPs, and the fluid flow around the tumor surface affect the penetration and accumulation of NPs into the tumor, through in vitro penetration study based on a spheroid-on-chip system. Surface decorated polystyrene (PS) NPs (100 nm) carrying positive and negative surface charge were loaded to the multicellular spheroids under static and flow conditions, in the presence or absence of serum proteins. NP penetration was investigated by confocal laser microscopy scanning followed with quantitative image analysis. The results reveal that negatively charged NPs are attached more on the spheroid surface and easier to penetrate into the spheroids. Protein corona, which is formed surrounding the NPs in the presence of serum protein, changes the surface properties of the NPs, weakens the NP-cell affinity, and, therefore, results in lower NP concentration on the spheroid surface but might facilitate deeper penetration. The exterior fluid flow enhances the interstitial flow into the spheroid, which benefits the penetration but also strips the NPs (especially the NPs with protein corona) on the spheroid surface, which decreases the penetration flux significantly. The maximal penetration was obtained by applying negatively charged NPs without protein corona under the flow condition. We hope the present study will help to understand the spatiotemporal performance of drug delivery NPs and inform the rational design of NPs with highly defined drug accumulation localized at a target site.

Fluorination in enhancing photoactivated antibacterial activity of Ru(ii) complexes with photo-labile ligands.

Fluorination in enhancing photoactivated antibacterial activity of Ru(ii) complexes with photo-labile ligands was studied. Ru(ii) polypyridine complexes containing a di-fluorinated dppz (dipyrido[3,2-a:2',3'-c]phenazine) or mono-trifluoromethylated dppz bidentate ligand and four pyridine monodentate ligands (complexes 3 and 4) were found to show potent photoactivated antibacterial activity against methicillin-resistant Staphylococcus aureus (MRSA), vancomycin-resistant Enterococcus (VRE), and Escherichia coli (E. coli) in both normoxic and hypoxic conditions. The bactericidal effect of complexes 3 and 4 under hypoxic conditions may stem from the fluorine-containing Ru(ii) aqua species after photo-induced pyridine dissociation, and DNA may be the potential antibacterial target. Photosensitized singlet oxygen may also account for their antibacterial activity under normoxic conditions. Moreover, negligible hemolysis rates as well as low dark- and photo-cytotoxicity toward human normal liver cells (L-O2) were also observed for both complexes. Our work may provide new insights into the development of novel and efficient Ru(ii) complex based photoactivatable antibacterial agents against antibiotic-resistant bacteria.

Fluorination on non-photolabile dppz ligands for improving Ru(ii) complex-based photoactivated chemotherapy.

Ru(ii) polypyridine complexes which can undergo photo-induced ligand dissociation and subsequent DNA covalent binding may potentially serve as photoactivated chemotherapeutic (PACT) agents. In this paper, three fluorinated dppz ligand coordinated Ru(ii) complexes (2-4) containing four monodentate pyridine ligands were studied. All complexes released one pyridine and covalently bound to DNA upon 470 nm irradiation. Compared with the parent complex [Ru(dppz)(py)4]2+ (1), 2-4 displayed enhanced phototoxicity but diminished dark cytotoxicity, more favorable for PACT application. Complex 3 is the most efficient one with IC50 values of about 8 µM toward HeLa and SKOV-3 cell lines, and also has a much higher IC50 value toward normal L-02 cells. Our results indicate that fluorination on the retaining ligand may be an efficient way to improve the drug activity of Ru(ii) PACT agents.